Rigid polyurethane foams

ABSTRACT

Process for making rigid polyurethane or urethane-modified polyisocyanurate foams comprising the step of reacting an organic polyisocyanate composition with an isocyanate-reactive composition comprising a polyester polyol in the presence of an amine catalyst characterized in that the pK a  of the conjugated ammonium salt of said amine is less than 12.

[0001] This invention relates to rigid polyurethane or urethane-modifiedpolyisocyanurate foams, to processes for their preparation and to polyolblends for use in said processes.

[0002] Rigid polyurethane and urethane-modified polyisocyanurate foamsare in general prepared by reacting a stoichiometric excess ofpolyisocyanate with isocyanate-reactive compounds in the presence ofblowing agents, surfactants and catalysts. One use of such foams is as athermal insulation medium in, for example, buildings.

[0003] Polyether polyols or polyester polyols are generally used asisocyanate-reactive compounds. Polyester polyols impart excellent flameretardancy characteristics to the resulting polyurethane foams and canin some cases even be less expensive than polyether polyols.

[0004] Tertiary amines are generally used as catalyst in rigidpolyurethane foam systems based on polyester polyols. A problemencountered when using tertiary amine catalysts in these polyester rigidfoam systems is that a cross-linked mass is obtained at a time when thefoam has not fully filled the cavity yet (for example, of a laminatedbuilding panel). This leads to dimensional stability problems due todensity distribution problems and cell stretching of the obtained foam.

[0005] Therefore it is an object of the present invention to provide aprocess for making rigid polyurethane foams based on polyester polyolsnot showing the disadvantages mentioned above.

[0006] According to the present invention a process for making rigidpolyurethane or urethane-modified polyisocyanurate foams is provided byreacting an organic polyisocyanate composition with anisocyanate-reactive composition comprising a polyester polyol in thepresence of an amine catalyst (B) characterised in that the pK_(a) ofthe conjugated ammoniumsalt of the amine (BH⁺) is less than 12,preferably less than 10, more preferably less than 8.

pK _(a) =−log K _(a) =−log [B][H ⁺ ]/[BH ⁺]

[0007] An acceptable rise profile is obtained having a fast initial foamrise leading to a smooth processability resulting in a better densitydistribution, lower minimum stable density and fill weights and highercompression strength of the foam.

[0008] Preferred catalysts to be used in the process of the presentinvention include aliphatic or aromatic tertiary amines preferablycontaining a supplemental heteroatom in the ring or functional groupshaving a positive inductive and/or positive mesomeric effect (forexample, alkyl groups or amino groups). Examples include2,2′-dimorpholinodiethylether, Texacat DP-914 (available from TexacoChemical), N,N-dimethylpiperazine, 1-methylimidazole,2-methyl-1-vinylimidazole, 1-allylimidazole, 1-phenylimidazole,1,2,4,5-tetramethylimidazole, 1(3-aminopropyl)imidazole, pyrimidazole,4-dimethylaminopyridine, 4-pyrrolidinopyridine, 4-morpholinopyridine,4-methylpyridine, N-dodecyl-2-methylimidazole and triazines such astris(dimethylaminopropyl)hexahydrotriazine. Especially preferredcatalysts are 2,2′-dimorpholinodiethylether, Texacat DP-914,1-methylimidazole and 4-dimethylaminopyridine. One or more of the abovedescribed catalysts can be used in the process of the present invention.

[0009] Some of the above described catalysts are known in polyurethanefoam production primarily for flexible foam production (see, forexample, U.S. Pat. No. 5,430,071, U.S. Pat. No. 3,645,925, U.S. Pat. No.3,661,808, U.S. Pat. No. 4,228,248, EP 672696, EP 401787). Their use inrigid polyurethane foam systems based on polyester polyols has not beendescribed heretobefore.

[0010] In general, the catalysts described above are used according tothe invention in an amount of between 0.05 and 5%, preferably between0.1 and 4% by weight based on the isocyanate-reactive composition.

[0011] In addition to the above described catalyst other catalysts knownin rigid polyurethane foam production can be used. These includealiphatic tertiary amines having pK_(a) values above 12. Examples ofadditional amine catalysts include dimethylbenzylamine,bis-dimethylaminoethylether (Niax A1 available from OSi) and pentamethyldiethylenetriamine (Desmorapid PV available from BASF). Especiallyaddition of Desmorapid PV is preferred; the reaction profile is furthersmoothen. Said additional catalysts are generally used in amountsvarying between 0.01 and 5%, preferably between 0.05 and 2% by weightbased on the isocyanate-reactive composition.

[0012] The term “polyester polyol” as used herein is meant to includeany polyester polyol having a hydroxyl functionality of at least twowherein the majority of the recurring units contain ester linkages andthe molecular weight is at least 400.

[0013] The polyester polyols for use in the present inventionadvantageously have an average functionality of about 1.8 to 8,preferably about 2 to 6 and more preferably about 2 to 2.5. Theirhydroxyl number values generally fall within a range of about 15 to 750,preferably about 30 to 550 and more preferably about 200 to 550 mgKOH/g. The molecular weight of the polyester polyol generally fallswithin the range of about 400 to about 10000, preferably about 1000 toabout 6000. Preferably the polyester polyols have an acid number between0.1 and 20 mg KOH/g; in general the acid number can be as high as 90 mgKOH/g.

[0014] The polyester polyols of the present invention can be prepared byknown procedures from a polycarboxylic acid or acid derivative, such asan anhydride or ester of the polycarboxylic acid, and any polyhydricalcohol. The polyacid and/or polyol components may be used as mixturesof two or more compounds in the preparation of the polyester polyols.

[0015] The polyols can be aliphatic, cycloaliphatic, aromatic and/orheterocyclic. Low molecular weight aliphatic polyhydric alcohols, suchas aliphatic dihydric alcohols having no more than about 20 carbon atomsare highly satisfactory. The polyols optionally may include substituentswhich are inert in the reaction, for example, chlorine and brominesubstituents, and/or may be unsaturated. Suitable amino alcohols, suchas, for example, monoethanolamine, diethanolamine, triethanolamine, orthe like may also be used. A preferred polyol component is a glycol. Theglycols may contain heteroatoms (e.g., thiodiglycol) or may be composedsolely of carbon, hydrogen and oxygen. They are advantageously simpleglycols of the general formula C_(n)H_(2n)(OH)₂ or polyglycolsdistinguished by intervening ether linkages in the hydrocarbon chain, asrepresented by the general formula C_(n)H_(2n)O_(x)(OH)₂. Examples ofsuitable polyhydric alcohols include: ethylene glycol, propylene glycol-(1,2) and -(1,3), butylene glycol -(1,4) and -(2,3), hexanediol -(1,6),octanediol -(1,8), neopentyl glycol, 1,4-bishydroxymethyl cyclohexane,2-methyl-1,3-propane diol, glycerin, trimethylolethane, hexanetriol-(1,2,6), butanetriol -(1,2,4), quinol, methyl glucoside,triethyleneglycol, tetraethylene glycol and higher polyethylene glycols,dipropylene glycol and higher polypropylene glycols, diethylene glycol,glycerol, pentaerythritol, trimethylolpropane, sorbitol, mannitol,dibutylene glycol and higher polybutylene glycols. Especially suitablepolyols are alkylene glycols and oxyalkylene glycols, such as ethyleneglycol, diethylene glycol, dipropylene glycol, triethylene glycol,tripropylene glycol, tetraethylene glycol, tetrapropylene glycol,trimethylene glycol, tetramethylene glycol and 1,4-cyclohexanedimethanol(1,4-bis-hydroxymethylcyclohexane).

[0016] The polycarboxylic acid component may be aliphatic,cycloaliphatic, aromatic and/or heterocyclic and may optionally besubstituted, for example, by halogen atoms and/or may be unsaturated.Examples of suitable carboxylic acids and derivatives thereof for thepreparation of the polyester polyols include: oxalic acid, malonic acid,adipic acid, glutaric acid, succinic acid, pimelic acid, suberic acid,azelaic acid, sebacic acid, phthalic acid, phthalic acid anhydride,terephthalic anhydride, isophthalic acid, terephthalic acid, trimelliticacid, tetrahydrophthalic acid anhydride, pyromellitic dianhydride,hexahydrophthalic acid anhydride, tetrachlorophthalic acid anhydride,endomethylene tetrahydrophthalic anhydride, glutaric acid anhydride,maleic acid, maleic acid anhydride, terephthalic acid dimethylester,terephthalic acid-bis glycol ester, fumaric acid, dibasic and tribasicunsaturated fatty acids optionally mixed with monobasic unsaturatedfatty acids, such as oleic acids.

[0017] While the polyester polyols can be prepared from substantiallypure reactant materials, more complex ingredients can be used, such asthe side-stream, waste or scrap residues from the manufacture ofphthalic acid, terephthalic acid, dimethyl terephthalate, polyethyleneterephthalate, and the like. These compositions can be converted byreaction with polyols to polyester polyols through conventionaltransesterification or esterification procedures.

[0018] The production of the polyester polyols is accomplished by simplyreacting the polycarboxylic acid or acid derivative with the polyolcomponent in a known manner until the hydroxyl and acid values of thereaction mixture fall in the desired range. After transesterification oresterification the reaction product can optionally be reacted with analkylene oxide.

[0019] The term “polyester polyol” as used herein includes any minoramounts of unreacted polyol remaining after the preparation of thepolyester polyol and/or unesterified polyol (e.g., glycol) added afterthe preparation. The polyester polyol can advantageously include up toabout 40% by weight free glycol. Preferably the free glycol content isfrom 2 to 30, more preferably from 2 to 15% by weight of the totalpolyester polyol component.

[0020] Aliphatic and/or aromatic polyester polyols can be used accordingto the present invention. Mixtures of two or more different polyesterpolyols may be used.

[0021] According to the present invention the polyester polyolsdescribed above can constitute the totality of the reactive mixturereacted with the polyisocyanate; it is understood, however, that thesepolyols could also be used mixed with other isocyanate-reactivecompounds conventionally used in the art; preferably at least 10% byweight, more preferably at least 20% by weight of the totalisocyanate-reactive compounds are polyester polyols as described above.

[0022] The isocyanate-reactive compounds which can be employed incombination with the polyester polyols in the preparation of the rigidpolyurethane foams of the present invention include any of those knownin the art for that purpose. Of particular importance for thepreparation of rigid foams are polyols and polyol mixtures havingaverage hydroxyl numbers of from 300 to 1000, especially from 300 to 700mg KOH/g, and hydroxyl functionalities of from 2 to 8, especially from 3to 8. Suitable polyols have been fully described in the prior art andinclude reaction products of alkylene oxides, for example ethylene oxideand/or propylene oxide, with initiators containing from 2 to 8 activehydrogen atoms per molecule. Suitable initiators include: polyols, forexample glycerol, trimethylolpropane, triethanolamine, pentaerythritol,sorbitol and sucrose; polyamines, for example ethylene diamine, tolylenediamine, diaminodiphenylmethane and polymethylene polyphenylenepolyamines; and aminoalcohols, for example ethanolamine anddiethanolamine; and mixtures of such initiators. Further suitablepolymeric polyols include hydroxyl terminated polythioethers,polyamides, polyesteramides, polycarbonates, polyacetals, polyolefinsand polysiloxanes.

[0023] Any of the blowing agents known in the art for the preparation ofrigid polyurethane or urethane-modified polyisocyanurate foams can beused in the process of the present invention. Such blowing agentsinclude water or other carbon dioxide-evolving compounds, or inert lowboiling compounds having a boiling point of above −70° C. at atmosphericpressure.

[0024] Where water is used as blowing agent, the amount may be selectedin known manner to provide foams of the desired density, typical amountsbeing in the range from 0.05 to 5% by weight based on the total reactionsystem.

[0025] Suitable inert blowing agents include those well known anddescribed in the art, for example, hydrocarbons, dialkyl ethers, alkylalkanoates, aliphatic and cycloaliphatic hydrofluorocarbons,hydrochlorofluorocarbons, chlorofluorocarbons, hydrochlorocarbons andfluorine-containing ethers.

[0026] Examples of preferred blowing agents include isobutane,n-pentane, isopentane, cyclopentane or mixtures thereof,1,1-dichloro-2-fluoroethane (HCFC 141b), 1,1,1-trifluoro-2-fluoroethane(HFC 134a), chlorodifluoromethane (HCFC 22),1,1-difluoro-3,3,3-trifluoropropane (HFC 245fa). Particular mention maybe made of blowing agent mixtures as described in PCT Patent PublicationNo. 96/12758, incorporated herein by reference, for manufacturing lowdensity, dimensionally stable rigid foam. These blowing agent mixturesgenerally comprise at least 3 and preferably at least 4 components ofwhich preferably at least one is a (cyclo)alkane (preferably of 5 or 6carbon atoms) and/or acetone.

[0027] The blowing agents are employed in an amount sufficient to givethe resultant foam the desired bulk density which is generally in therange 15 to 70 kg/m³, preferably 20 to 50 kg/m³, most preferably 25 to40 kg/m³. Typical amounts of blowing agents are in the range 2 to 25% byweight based on the total reaction system.

[0028] When a blowing agent has a boiling point at or below ambient itis maintained under pressure until mixed with the other components.Alternatively, it can be maintained at subambient temperatures untilmixed with the other components.

[0029] Other optional additives for the polyol blends of the presentinvention include crosslinking agents, for examples low molecular weightpolyols such as triethanolamine, processing aids, viscosity reducers,dispersing agents, plasticizers, mold release agents, antioxidants,fillers (e.g. carbon black), cell size regulators such as insolublefluorinated compounds (as described, for example, in U.S. Pat. No.4,981,879, U.S. Pat. No. 5,034,424, U.S. Pat. No. 4,972,002, EP 0508649,EP 0498628, WO 95/18176), non-amine polyurethane catalysts (e.g.stannous salts of carboxylic acids), trimerisation catalysts (e.g.alkali metal carboxylic acid salts), surfactants such aspolydimethylsiloxanepolyoxyalkylene block copolymers and non-reactiveand reactive fire retardants, for example halogenated alkyl phosphatessuch as tris chloropropyl phosphate, triethylphosphate,diethylethylphosphonate and dimethylmethylphosphonate. The use of suchadditives is well known to those skilled in the art.

[0030] Another useful additive particularly to further improve thereaction profile is an organic carboxylic acid, especially a carboxylicacid containing at least one OH, SH, NH₂ or NHR functional group,wherein R is an alkyl, cycloalkyl or aryl group. Such carboxylic acidshave the general formula X_(n)—R′—(COOH)_(m) wherein X is OH, SH, NH₂ orNHR, R′ is an at least divalent hydrocarbon moiety, typically an atleast divalent linear or branched aliphatic hydrocarbon moiety and/or anat least divalent alicyclic or aromatic hydrocarbon moiety, n is aninteger having a value of at least 1 and allows for mono andpolyfunctional substitution on the hydrocarbon moiety, m is an integerhaving a value of at least 1 and allows for mono and polycarboxylsubstitution on the hydrocarbon moiety. The “at least divalenthydrocarbon moiety” can be a saturated or unsaturated moiety of 1 to 20carbon atoms, including a linear aliphatic moiety, a branched aliphaticmoiety, an alicyclic moiety or an aromatic moiety. Stated otherwise, R′can, for example, be a linear or branched alkylene group of 1 to 10carbon atoms, a cyclic alkylene group of 4 to 10 carbon atoms, or anarylene, an alkarylene or an ararylene group of 6 to 20 carbon atoms.Specific non-limiting examples of suitable hydrocarbon moieties aremethylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene,n-amylene, n-decylene, 2-ethylhexylene, o-, m-, p-phenylene,ethyl-p-phenylene, 2,5-naphthylene, p,p′-biphenylene, cyclopentylene,cycloheptylene, xylylene, 1,4-dimethylenephenylene and the like. Whileabove-noted radicals have two available substitution sites, at least onefor a carboxyl group and one for a OH, SH, NH₂ or NHR group, it iscontemplated that additional hydrogens on the hydrocarbon could bereplaced with further carboxyl and/or OH, SH, NH₂ or NHR groups. Suchcarboxylic acids generally have molecular weights below about 250. Thefollowing carboxylic acids are especially suitable: citric acid,dimethylolpropionic acid, 2-hydroxymethylpropionic acid,bishydroxypropionic acid, salicylic acid, m-hydroxy benzoic acid,p-hydroxy benzoic acid, dihydroxybenzoic acid, glycolic acid,β-hydroxybutyric acid, cresotic acid, 3-hydroxy-2-naphthoic acid, lacticacid, tartaric acid, malic acid, resorcylic acid, hydroferulic acid,glycine, alanine, mercaptoacetic acid and the like. Preferably X is OH,n is 1, R′ is a linear or branched aliphatic hydrocarbon having 1 to 5carbon atoms and m is 1, 2 or 3. Most preferred carboxylic acids arelactic acid, glycolic acid, malic acid and citric acid. At least one ofsaid carboxylic acids is used; mixtures of two or more of these acidscan be used as well. Particularly preferred carboxylic acids are malicacid or a combination of malic acid and citric acid, preferably in aweight ratio of between 75:25 and 25:75, most preferably in a weightratio of about 1:1. The carboxylic acid is generally used in an amountranging from 0.1 to 5% by weight based on the isocyanate-reactivecomposition, preferably about 1% to 3%.

[0031] Suitable organic polyisocyanates to be reacted with theisocyanate-reactive composition to form rigid polyurethane orurethane-modified polyisocyanurate foams include any of those known inthe art for the preparation of rigid polyurethane or urethane-modifiedpolyisocyanurate foams, and in particular the aromatic polyisocyanatessuch as diphenylmethane diisocyanate in the form of its 2,4′-, 2,2′- and4,4′-isomers and mixtures thereof, the mixtures of diphenylmethanediisocyanates (MDI) and oligomers thereof known in the art as “crude” orpolymeric MDI (polymethylene polyphenylene polyisocyanates) having anisocyanate functionality of greater than 2, toluene diisocyanate in theform of its 2,4- and 2,6-isomers and mixtures thereof, 1,5-naphthalenediisocyanate and 1,4-diisocyanatobenzene. Other organic polyisocyanateswhich may be mentioned include the aliphatic diisocyanates such asisophorone diisocyanate, 1,6-diisocyanatohexane and4,4′-diisocyanatodicyclohexylmethane. Further suitable polyisocyanatesfor use in the process of the present invention are those described inEP-A-0320134. Modified polyisocyanates, such as carbodiimide oruretonimine modified polyisocyanates can also be employed. Still otheruseful organic polyisocyanates are isocyanate-terminated prepolymersprepared by reacting excess organic polyisocyanate with a minor amountof an active hydrogen-containing compound. Preferred polyisocyanates tobe used in the present invention are the polymeric MDI's.

[0032] The quantities of the polyisocyanate composition and thepolyfunctional isocyanate-reactive composition to be reacted can bereadily determined by the man skilled in the art. In general the NCO:OHratio falls within the range 0.85 to 1.40, preferably about 0.98 to1.20. Also higher NCO:OH ratios (for example, up to 3.0) fall within thepresent invention.

[0033] In operating the process for making rigid foams according to theinvention, the known one-shot, prepolymer or semi-prepolymer techniquesmay be used together with conventional mixing methods and the rigid foammay be produced in the form of slabstock, mouldings, cavity fillings,sprayed foam, frothed foam or laminates with other materials such ashardboard, plasterboard, plastics, paper or metal.

[0034] It is convenient in many applications to provide the componentsfor polyurethane production in pre-blended formulations based on each ofthe primary polyisocyanate and isocyanate-reactive components. Inparticular, many reaction systems employ a polyisocyanate-reactivecomposition which contains the major additives such as the catalyst andthe blowing agent in addition to the polyisocyanate-reactive componentor components.

[0035] Therefore the present invention also provides a polyfunctionalisocyanate-reactive composition comprising a polyester polyol and anamine catalyst as defined above.

[0036] In order to stabilise said pre-blended systems (preferablyhydroxy-)functionalised carboxylic acids as described above arepreferably added.

[0037] The foams of the present invention are advantageously used forproducing laminates whereby the foam is provided on one or both sideswith a facing sheet. The laminates are advantageously made in acontinuous or discontinuous manner by depositing the foam-formingmixture on a facing sheet and preferably placing another facing sheet onthe deposited mixture. Any facing sheet previously employed to producebuilding panels can be employed and can be of a rigid or flexiblenature.

[0038] The various aspects of this invention are illustrated, but notlimited by the following examples in which the following ingredients areused:

[0039] Polyol A: a sorbitol initiated polyether polyol of OH value 460mg KOH/g.

[0040] Polyol B: an aliphatic polyester polyol of OH value 356 mg KOH/g.

[0041] Polyol C: an aromatic amine initiated polyether polyol of OHvalue 495 mg KOH/g.

[0042] Polyol D: a brominated polyether polyol of OH value 310 mg KOH/g.

[0043] Polyol E: an aromatic polyester polyol of OH value 241 mg KOH/g.

[0044] Polyol F: an aliphatic polyester polyol of OH value 575 mg KOH/g.

[0045] Polyol G: a glycerol initiated polyether polyol of OH value 1122mg KOH/g.

[0046] Fire retardant A: a chlorinated flame retardant.

[0047] Fire retardant B: a phosphorous based flame retardant.

[0048] Surfactant A: a silicone surfactant.

[0049] Surfactant B: a silicone surfactant.

[0050] DMP: dimethylpiperazine catalyst available from Aldrich.

[0051] NP: N-methyl-N′-2(dimethyl)aminoethylpiperazine catalystavailable from Toyosoda Manufacturing.

[0052] NMM: N-methylmorpholine catalyst available from Janssen Chemica.

[0053] DMEA: N,N-dimethylethanolamine catalyst available from AirProducts.

[0054] MM: 4(2-methoxyethyl)morpholine catalyst available from Huntsman.

[0055] NBM: N-butylmorpholine catalyst available from Huntsman.

[0056] NEM: N-ethylmorpholine catalyst available from Aldrich.

[0057] TEA: triethylamine catalyst available from BASF.

[0058] DMBA: dimethylbenzylamine catalyst available from Protex.

[0059] DMDEE: dimorpholinodiethylether catalyst available from Nitroil.

[0060] DMAP: dimethylaminopyridine catalyst available from Aldrich.

[0061] NMI: N-methyl imidazole catalyst available from BASF.

[0062] Polycat 41: tris(dimethylaminopropyl)hexahydrotriazine catalystavailable from Air Products.

[0063] Polycat 43: an amine based catalyst salt available from AirProducts.

[0064] Polycat 46: a potassium acetate catalyst available from AirProducts.

[0065] Catalyst LB: a potassium acetate catalyst available from Bayer.

[0066] Niax A1: bis(dimethylaminoethyl)ether catalyst available fromOSi.

[0067] Texacat DP914: a catalyst available from Texaco.

[0068] DMCHA: dimethylcyclohexylamine catalyst available from BASF.

[0069] Desmorapid PV: pentamethyldiethylenetriamine catalyst availablefrom BASF.

[0070] DBTDL: dibutyltindilaurate catalyst.

[0071] SUPRASEC DNR: polymeric MDI available from Imperial ChemicalIndustries.

[0072] SUPRASEC 2085: polymeric MDI available from Imperial ChemicalIndustries.

[0073] SUPRASEC is a trademark of Imperial Chemical Industries.

EXAMPLE 1

[0074] Rigid polyurethane foams were made from a polyol composition anda polyisocyanate composition containing the ingredients listed below inTable 1 at an NCO index of 1.15. The reaction profile was followed inrespect of cream time (time taken for the reaction mixture to startfoaming) and string time (time taken for the reaction mixture to reachthe transition point from fluid to cross-linked mass). The height ofexpansion was measured at the string time and also at the end of rise ofthe foam; from those two figures the expansion factor at string time(height at string/height at end of rise) was determined. The results arealso given in Table 1. The rise profile was also followed by DynamicFlow Data analysis. Results are presented in FIGS. 1 and 2 expressingthe height of the rising foam versus the reaction time.

[0075] These results show that using amine catalysts according to thepresent invention (Foams no. 2 to 6) leads to improved reaction profilescompared to foams of the prior art (Foam No. 1) (see FIG. 1). Additionof selected classes of other catalysts such as Desmorapid PV (Foam No.7) further improves the reaction profile (see FIG. 2). TABLE 1 Foam No.1 2 3 4 5 6 7 8 POLYOL Polyol A pbw 20.5 20.5 20.5 20.5 20.5 20.5 20.520.5 Polyol B pbw 23.0 23.0 23.0 23.0 23.0 23.0 23.0 23.0 Polyol C pbw10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Polyol D pbw 21.0 21.0 21.0 21.021.0 21.0 21.0 21.0 glycolic acid pbw 1.0 lactic acid pbw 1.1 1.1 1.11.1 1.1 1.1 Fire retardant A pbw 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Fireretardant B pbw 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Surfactant A pbw 2.0 2.02.0 2.0 2.0 2.0 2.0 2.0 Desmorapid PV pbw 0.4 DMBA pbw 1.0 1.0 1.0 1.01.0 1.0 1.0 1.0 DMDEE pbw 1.5 0.4 1.5 DMAP pbw 0.3 NMI pbw 0.3 Polycat41 pbw 0.7 Niax Al pbw 0.15 Texacat DP914 pbw 0.5 DMCHA pbw 0.80 waterpbw 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 HCFC 141b pbw 4.2 4.2 4.2 4.2 4.24.2 4.2 4.2 POLYISOCYANATE SUPRASEC DNR pbw 139 139 139 139 139 139 139139 Cream time sec 17 17 20 16 17 18 17 13 String time sec 154 120 134131 141 137 129 127 Expansion factor % 93 89 90 86 90 84 98 95 at stringtime

EXAMPLE 2

[0076] Rigid polyurethane foams were made from a polyol composition anda polyisocyanate composition containing the ingredients listed below inTable 2 at an NCO index of 2.20. The reaction profile was followed inrespect of cream time (time taken for the reaction mixture to startfoaming) and string time (time taken for the reaction mixture to reachthe transition point from fluid to cross-linked mass). The height ofexpansion was measured at the string time and also at the end of rise ofthe foam; from those two figures the expansion factor at string time(height at string/height at end of rise) was determined. The results arealso given in Table 2. The rise profile was also followed by DynamicFlow Data analysis. Results are presented in FIG. 3 expressing theheight of the rising foam versus the reaction time.

EXAMPLE 3

[0077] Panels were made from the formulations 1, 2 and 7 as defined inTable 1 using a high pressure machine (Hennecke HK 650). Temperature ofthe chemicals: 20° C.; output: 681 g/sec; pressure: 150 bar. Ahorizontal mould of dimensions 330×100×10 cm was used with injectionsidewards (right hand side) at the initial part thereof. Temperature ofthe mould: 37° C. Foams were made to an overpack density of 40 to 41g/l. Foam No. 7 was also made at even higher overpack (Foam No. 7 bis).The following measurements were done on the obtained moulded foams: coreand overall density (according to standard ISO 845) in the left andright hand corner of the initial part of the mould (injection part) andof the final part of the mould (end of the panel), compression strengthin the three dimensions (according to standard ISO 844) in the centre ofthe initial part and in the centre of the final part, dimensionalstability (according to standard ISO 2796) of the panels (final part)after storage for 24 hours at room temperature and another 48 hours at−25° C., at 70° C. and 90% relative humidity and at 100° C.,respectively. The results are given in Table 3.

[0078] These results show that foams according to the present invention(Foams No. 2 and 7) have a better density distribution profile thanfoams of the prior art (Foam No. 1); less variation in density isobtained over the whole of the panel. Also the compression strength ismore uniform over the whole panel. Further improvements are obtained byadding Desmorapid PV (Foam No. 7 vis-a-vis Foam No. 2). TABLE 2 Foam No.9 10 POLYOL Polyol E pbw 55.4 55.4 Polyol B pbw 28.5 28.5 Polyol F pbw6.7 6.7 Surfactant B pbw 1.9 1.9 Polycat 43 pbw 0.5 0.5 Catalyst LB pbw1.2 1.2 water pbw 1.0 1.0 Polyol G pbw 4.8 4.8 Niax Al pbw 0.3 DMCHA pbw0.6 DMDEE pbw 2.0 Desmorapid PV pbw 0.8 HCFC 141b pbw 25 25POLYISOCYANATE SUPRASEC 2085 pbw 220 220 Density g/l 33.0 29.0 Creamtime sec 18 15 String time sec 47 48 Expansion factor at % 83.7 89.8string time

[0079] TABLE 3 Foam No. 1 2 7 7 bis Cream time sec 17 10 12 String timesec 154 88 86 Free rise density g/l 23.2 23.7 23.7 overall/core densityInitial right hand g/l 41.5/38.5 40.5/37.3 38.5/37.2 40.7/37.4 cornerInitial left hand g/l 40.9/38.2 40.2/38.1 38.9/38.7 39.3/37.5 cornerFinal right hand g/l 39.9/33.2 41.6/34.9 38.6/35.4 39.9/36.1 cornerFinal left hand g/l 40.2/34.2 40.3/33.9 36.8/35.1 40.7/37.2 cornerAverage g/l 40.6/36.0 40.6/36.0 38.7/36.6 40.1/37.0 Compression strengthInitial length kPa 235 245 211 248 Initial thickness kPa 193 176 170 174Initial width kPa 182 193 161 180 Initial average kPa 203 205 181 200Initial density g/l 37.3 36.7 37.6 35.5 Final length kPa 135 143 134 163Final thickness kPa 181 191 212 220 Final width kPa 79 86 176 202 Finalaverage kPa 131 140 174 195 Final density g/l 33.2 34.1 34.0 35.2Dimensional stability at −25° C. % 0.15 0.2 −0.3 −0.3 at 70° C. % −12.5−13.1 −7.5 −4.2 (RH 90%) at 100° C. % −3.2 −4.7 −2.7 −2.2

EXAMPLE 4

[0080] Rigid polyurethane foams were made from a polyol composition anda polyisocyanate composition containing the ingredients listed below inTable 4 at an NCO index of 1.15. The reaction profile was followed inrespect of cream time (time taken for the reaction mixture to startfoaming) and string time (time taken for the reaction mixture to reachthe transition point from fluid to cross-linked mass). The height ofexpansion was measured at the string time and also at the end of rise ofthe foam; from those two figures the expansion factor at string time(height at string/height at end of rise) was determined. The results arealso given in Table 4. These results show that the best results areobtained when dimorpholinodiethylether or N-ethylmorpholine is used ascatalyst.

EXAMPLE 5

[0081] Rigid polyurethane foams were made from a polyol composition anda polyisocyanate composition containing the ingredients listed below inTable 5 at an NCO index of 1.15. The reaction profile was followed inrespect of cream time (time taken for the reaction mixture to startfoaming) and string time (time taken for the reaction mixture to reachthe transition point from fluid to cross-linked mass). The height ofexpansion was measured at the string time and also at the end of rise ofthe foam; from those two figures the expansion factor at string time(height at string/height at end of rise) was determined. The results arealso given in Table 5. TABLE 4 Foam No. 11 12 13 14 15 16 17 18 19POLYOL Polyol A pbw 20.5 20.5 20.5 20.5 20.5 20.5 20.5 20.5 20.5 PolyolB pbw 23.0 23.0 23.0 23.0 23.0 23.0 23.0 23.0 23.0 Polyol C pbw 10.010.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Polyol D pbw 21.0 21.0 21.0 21.021.0 21.0 21.0 21.0 21.0 lactic acid pbw 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.11.0 Fire retardant A pbw 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Fireretardant B pbw 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Surfactant A pbw 2.02.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 DMBA pbw 1 1 1 1 1 1 1 1 0.6 DMDEE pbw1.5 DMP pbw 0.65 NP pbw 0.6 NMM pbw 1.5 DMEA pbw 0.6 DMAP pbw 0.3 MM pbw3 NBM pbw 3.1 NEM pbw 1.5 water pbw 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3HCFC 141b pbw 4.2 4.2 4.2 4.2 4.2 4.2 4.2 4.2 4.2 POLYISOCYANATESUPRASEC DNR pbw 139 139 139 139 139 139 139 139 139 Cream time sec 2040 37 29 37 33 29 19 String time sec 110 113 107 92 112 109 92 115Expansion factor % 91.7 85.8 85.5 90.5 at string time

[0082] TABLE 5 Foam No. 20 21 22 23 24 25 26 27 28 29 30 31 POLYOLPolyol A pbw 20.5 20.5 20.5 20.5 20.5 20.5 20.5 20.5 20.5 20.5 20.5 20.5Polyol B pbw 23.0 23.0 23.0 23.0 23.0 23.0 23.0 23.0 23.0 23.0 23.0 23.0Polyol C pbw 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0Polyol D pbw 21.0 21.0 21.0 21.0 21.0 21.0 21.0 21.0 21.0 21.0 21.0 21.0malic acid pbw 1 1 1 1 1 1 1 1 1 1 1 1 Fire retardant A pbw 8.3 8.3 8.38.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Fire retardant B pbw 8.3 8.3 8.3 8.38.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Surfactant B pbw 2.0 2.0 2.0 2.0 2.0 2.02.0 2.0 2.0 2.0 2.0 2.0 DMBA pbw 0.6 1 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.60.6 0.6 DMDEE pbw 1.5 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 DBTDLpbw 0.05 0.03 0.02 NMI pbw 0.2 TEA pbw 0.3 0.3 Niax Al pbw 0.4 Polycat46 pbw 0.5 Desmorapid PV pbw 0.4 0.2 DMCHA pbw 0.3 Polycat 41 pbw 0.4water pbw 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 HCFC 141b pbw4.2 4.2 4.2 4.2 4.2 4.2 4.2 4.2 4.2 4.2 4.2 4.2 POLYISOCYANATE SUPRASECDNR 139 139 139 139 139 139 139 139 139 139 139 139 Cream time sec 14 1616 17 14 14 17 15 13 15 15 18 String time sec 107 114 105 114 112 89 115120 107 110 113 105 Expansion factor % 91.4 89.2 90.7 89.7 89.6 89.491.1 90.9 90.1 at string time

1. Process for making rigid polyurethane or urethane-modifiedpolyisocyanurate foams comprising the step of reacting an organicpolyisocyanate composition with an isocyanate-reactive compositioncomprising a polyester polyol in the presence of an amine catalystcharacterised in that the pK_(a) of the conjugated ammonium salt of saidamine is less than
 12. 2. Process according to claim 1 wherein thepK_(a) is less than
 10. 3. Process according to claim 1 or 2 whereinsaid amine catalyst is selected from the group consisting of2,2′-dimorpholinodiethylether, 1-methylimidazole,4-dimethylaminopyridine, Texacat DP-914 andtris(dimethylaminopropyl)hexahydrotriazine.
 4. Process according to anyone of the preceding claims wherein said amine catalyst is used in anamount of between 0.05 and 5% by weight based on the isocyanate-reactivecomposition.
 5. Process according to any one of the preceding claimswherein an additional tertiary amine catalyst is used.
 6. Processaccording to claim 5 wherein said additional catalyst ispentamethyldiethylenetriamine.
 7. Process according to claim 5 or 6wherein said additional catalyst is used in an amount of between 0.01and 5% by weight based on the isocyanate-reactive composition. 8.Process according to any one of the preceding claims wherein thepolyester polyol has an average functionality of 1.8 to 8, a hydroxylnumber of 15 to 750 mg KOH/g and a molecular weight of 400 to
 10000. 9.Process according to any one of the preceding claim wherein thepolyester polyol constitutes at least 10% by weight of the totalisocyanate-reactive compounds.
 10. Process according to any one of thepreceding claims wherein said reaction is carried out in the presence ofan organic hydroxy functionalised carboxylic acid.
 11. Process accordingto claim 10 wherein said hydroxy functionalised carboxylic acid isselected from the group consisting of lactic acid, glycolic acid, malicacid, citric acid.
 12. Process according to claim 11 wherein ascarboxylic acid is used a mixture of citric acid and malic acid in aweight ratio of about 1:1.
 13. Process according to claim 10 , 11 or 12wherein said hydroxy functionalised carbxylic acid is used in an amountranging from 0.1 to 5% by weight based on the isocyanate-reactivecomposition.
 14. Rigid polyurethane or urethane-modifiedpolyisocyanurate foams obtainable by the process as defined in any oneof the preceding claims.
 15. Isocyanate-reactive composition comprisinga polyester polyol and an amine catalyst chareacterised in that saidamine catalyst is as defined in any one of claims 1 to 4 . 16.Isocyanate-reactive composition according to claim 15 wherein saidcomposition further comprises a hydroxy functionalised organiccarboxylic acid as defined in any one of claims 10 to 13 .